Low Common Mode Noise Transformers And Switch-Mode DC-DC Power Converters

ABSTRACT

A switch-mode DC-DC power converter includes one or more input terminals and output terminals, and a transformer coupled between the input and output terminals. The transformer includes a plurality of winding sets. Each winding set includes a primary winding and a secondary winding magnetically coupled with one another. The primary winding and the secondary winding include the same number of turns. The primary windings of the plurality of winding sets are connected in series and the secondary windings of the plurality of winding sets are connected in parallel. The power converter also includes at least one spacer positioned to separate an adjacent pair of the plurality of winding sets. A magnetic coupling between the adjacent pair of the plurality of winding sets is less than the magnetic coupling between the primary winding and the secondary winding within each winding set.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.16/293,231 filed Mar. 5, 2019. The entire disclosure of the aboveapplication is incorporated herein by reference.

FIELD

The present disclosure relates to low common mode noise transformers andswitch-mode DC-DC power converters.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Growing power demands for cloud computing, data centers, etc. arerequiring power supplies with increased power efficiency and increasedpower density. Power efficiency is commonly limited by magnetic corelosses due to proximity and eddy current in copper wires at highfrequency. In addition, common mode noise is increased at high frequencydue to a higher change in voltage over time in transformer windings.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

According to one aspect of the present disclosure, a switch-mode DC-DCpower converter includes one or more input terminals for receiving aninput voltage from a voltage source, one or more output terminals forsupplying an output voltage to a load, and a transformer coupled betweenthe input and output terminals. The transformer includes a plurality ofwinding sets. Each winding set includes a primary winding and asecondary winding magnetically coupled with one another. The primarywinding and the secondary winding include the same number of turns. Theprimary windings of the plurality of winding sets are connected inseries and the secondary windings of the plurality of winding sets areconnected in parallel. The power converter also includes at least onespacer positioned to separate an adjacent pair of the plurality ofwinding sets. A magnetic coupling between the adjacent pair of theplurality of winding sets is less than the magnetic coupling between theprimary winding and the secondary winding within each winding set.

According to another aspect of the present disclosure, an interleavedLLC power converter one or more input terminals for receiving an inputvoltage from a voltage source, one or more output terminals forsupplying an output voltage to a load, and a first LLC converter. Thefirst LLC converter includes a first transformer and a first spacer. Thefirst transformer is coupled between the input and output terminals, andincludes a first plurality of winding sets each including a primarywinding and a secondary winding magnetically coupled with one another.The first spacer is positioned to separate an adjacent pair of the firstplurality of winding sets. The primary windings of the first pluralityof winding sets are connected in series and the secondary windings ofthe first plurality of winding sets are connected in parallel. The powerconverter also includes a second LLC converter interleaved with thefirst LLC converter. The second LLC converter includes a secondtransformer and a second spacer. The second transformer is coupledbetween the input and output terminals, and includes a second pluralityof winding sets each including a primary winding and a secondary windingmagnetically coupled with one another. The second spacer is positionedto separate an adjacent pair of the second plurality of winding sets.The primary windings of the second plurality of winding sets areconnected in series and the secondary windings of the second pluralityof winding sets are connected in parallel.

According to yet another aspect of the present disclosure, a transformerincludes at least one core, and a plurality of winding sets wound aboutthe at least one core. Each winding set includes a primary winding and asecondary winding magnetically coupled with one another. The primarywinding and the secondary winding include the same number of turns. Theprimary windings of the plurality of winding sets are connected inseries and the secondary windings of the plurality of winding sets areconnected in parallel to define a step-down turns ratio of thetransformer, or the primary windings of the plurality of winding setsare connected in parallel and the secondary windings of the plurality ofwinding sets are connected in series to define a step-up turns ratio ofthe transformer. The transformer also includes at least one spacerpositioned to separate an adjacent pair of the plurality of windingsets, and a plurality of rectifiers. A magnetic coupling between theadjacent pair of the plurality of winding sets is less than the magneticcoupling between the primary winding and the secondary winding withineach winding set.

Further aspects and areas of applicability will become apparent from thedescription provided herein. It should be understood that variousaspects of this disclosure may be implemented individually or incombination with one or more other aspects. It should also be understoodthat the description and specific examples herein are intended forpurposes of illustration only and are not intended to limit the scope ofthe present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a circuit diagram of a switch-mode DC-DC power converter,according to one example embodiment of the present disclosure.

FIG. 2 is a circuit diagram of a switch-mode DC-DC power converter,according to another example embodiment of the present disclosure

FIG. 3 is a circuit diagram of an interleaved LLC power converter,according to another example embodiment of the present disclosure.

FIG. 4 is an exploded view of a transformer, according to anotherexample embodiment of the present disclosure.

FIG. 5 is an exploded view of a transformer including a resonantinductor coil, according to another example embodiment of the presentdisclosure.

FIG. 6 is a circuit diagram of a transformer, according to anotherexample embodiment of the present disclosure.

Corresponding reference numerals indicate corresponding parts orfeatures throughout the several views of the drawings.

DETAILED DESCRIPTION

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

Example embodiments will now be described more fully with reference tothe accompanying drawings.

A switch-mode DC-DC power converter according to one example embodimentis illustrated in FIG. 1 and indicated generally by reference 100. Thepower converter 100 includes input terminal(s) 102 for receiving aninput voltage from a voltage source, and output terminal(s) 104 forsupplying an output voltage to a load.

The power converter 100 also includes a transformer 110 coupled betweenthe input and output terminals 102 and 104. The transformer 110 includestwo winding sets. The first winding set includes a primary winding 112and a secondary winding 114, and the second winding set includes aprimary winding 116 and a secondary winding 118.

The primary winding 112 is magnetically coupled with the secondarywinding 114 (e.g., via a tight coupling, etc.). The primary winding 112and the secondary winding 114 may have the same number of turns.Similarly, the primary winding 116 is magnetically coupled with thesecondary winding 118 (e.g., via a tight coupling, etc.). The primarywinding 116 and the secondary winding 118 may have the same number ofturns.

The power converter 100 also includes a spacer 120 positioned toseparate the plurality of winding sets, which are adjacent one another.Due to the position of the spacer 120, magnetic coupling between theadjacent pair of the plurality of winding sets (e.g., a loose coupling,etc.) is less than the magnetic coupling between the primary winding andthe secondary winding within each winding set (e.g., a tight coupling,etc.).

The primary windings 112 and 116 are connected in series, and thesecondary windings 114 and 118 are connected in parallel. For example,the power converter 100 includes optional rectifiers 134 and 136, andthe secondary windings 114 and 118 are connected in parallel via theoptional rectifiers 134 and 136.

Specifically, the optional rectifier 134 is coupled between thesecondary winding 114 and the output terminals 104, and the rectifier136 is coupled between the secondary winding 118 and the outputterminals 104. Outputs of the rectifiers 134 and 136 are connected inparallel. In other embodiments, the secondary windings 114 and 118 maybe connected in parallel directly (e.g., as illustrated in FIG. 2 anddescribed below).

The power converter 100 reduces (e.g., minimizes) common mode noise dueto parasitic capacitance between the primary windings 112 and 116 andthe secondary windings 114 and 118, while providing high powerefficiency at high switching frequencies.

For example, as mentioned above the primary windings 112 and 116 mayeach have the same number of turns as their corresponding secondarywindings 114 and 118. Each primary winding 112 and 116 is tightlycoupled (e.g., magnetically) with its corresponding secondary winding114 and 118, while the spacer 120 separates the adjacent sets ofwindings to create loose coupling (e.g., magnetically) between theadjacent sets of windings.

If the number of turns of each primary winding 112 and 116 is the sameas its corresponding secondary winding 114 and 118, a voltage changeover time (dV/dt) of each winding may be matched to reduce (e.g.,minimize) common mode current due to parasitic capacitance between thecorresponding primary and secondary winding. Tightly coupled primary andsecondary windings with a turns ratio of 1:1 may lower AC resistance ofeach set of windings while the other set of windings is separated by thespacer 120.

As illustrated in FIG. 1, the power converter 100 includes two switchesQ1 and Q2, two capacitors C1 and C2, and an inductor L1. Although FIG. 1illustrates two capacitors C1 and C2, other embodiments may include onlyone capacitor on the primary side (e.g., as illustrated in FIG. 2 anddescribed below), more than two capacitors on the primary side, etc.

The switches Q1 and Q2, the capacitors C1 and C2, and the inductor L1are coupled between the input terminals 102 and the primary windings 112and 116. Specifically, the switches Q1 and Q2 are coupled in parallelwith the capacitors C1 and C2, and the inductor L1 is coupled betweenthe capacitors C1 and C2 and the primary windings 112 and 116.

If each primary winding 112 and 116 has the same number of turns as itscorresponding secondary winding 114 and 118, each set of correspondingprimary and secondary windings will have a 1:1 turns ratio. Because theprimary windings are connected in series while the secondary windingsare connected in parallel via the rectifiers 134 and 136, the powerconverter 100 will have a 2:1 transformer turns ratio.

In other embodiments, the turns ratio for the power converter 100 may beadjusted by increasing or decreasing the number of sets of windings inthe power converter 100, while maintaining the series connection of allprimary windings and the parallel connection of all secondary windingsvia the rectifiers. For example, if a power converter includes four setsof primary and secondary windings, the power converter may have a 4:1transformer turns ratio. Other embodiments may have a higher or lowerturns ratio, such as 1:1, 3:1, 5:1, 8:1, etc.

The input voltage may be set as an integer multiple of a desired outputvoltage, assuming little or no resistive voltage drops due to windings,primary field-effect transistors (FETs), etc. Specifically, the inputvoltage (Vin) may be equal to the output voltage (Vo) times a number ofsets of windings in the converter.

As an example, for a 48V output, the input voltage may be 48V, 96V,144V, etc. If a PFC pre-regulator is used (e.g., for variable outputvoltage applications, etc.), the output voltage for a 230V nominal inputmay be selected as 384V. Using a half-bridge LLC topology, the inputvoltage would be 384/2=192V. In that case, a 4:1 transformer turns ratiowould provide an output voltage of 48V. As described above, four 1:1primary and secondary winding sets (e.g., coils) may be used to realizethe 4:1 transformer turns ratio by connecting the primary windings ofthe four sets in series while connecting the secondary windings inparallel.

In order to accommodate resistive drops due to load current, the inputvoltage may need to be increased, an LLC operating frequency may need tobe set lower than the resonant frequency, etc. The required operationfrequency adjustment to compensate for the resistive voltage drops maydepend on an LLC gain versus frequency characteristics, etc. Although anoutput voltage of 48V DC is described as an example herein, otherembodiments may use any other suitable input or output voltages, such as12V DC, etc. The power converter includes an optional output capacitorC5 coupled in parallel with the output terminals 104. Other embodimentsmay include more than one output capacitor, no output capacitor, etc.

The power converter 100 may include one or more controllers forcontrolling switching operation of the switches Q1 and Q2. For example,the controller may control switching operation of the switches Q1 and Q2to conduct the input voltage with two half cycles, where all of saidwindings conduct current for the load (e.g., load related current)during both half cycles. The two half cycles may correspond to positiveand negative phases of an AC voltage, etc.

The controller(s) may control switching operation of the switches Q1 andQ2 to operate with any suitable switching frequency, such as a switchingfrequency above 20 kHz, above 100 kHz, above 400 KHz, about one MHz,etc.

As mentioned above, the power converter 100 may provide high powerefficiency while operating at high switching frequencies. For example,the controller(s) may control switching operation of the switches Q1 andQ2 of the LLC converters 106 and 108 to operate with any suitable powerefficiency, such as a power efficiency greater than 90%, greater than95%, in a range between 98% and 99%, etc.

Although FIG. 1 illustrates a specific LLC arrangement of the capacitorsand inductors, other embodiments may include LLC converters includingmore or less capacitors and inductors, inductors and capacitorsconnected in different LLC circuit arrangements, etc.

For example, FIG. 2 illustrates an example switch-mode power converter200 including a single capacitor C1 between the input terminals 102 andthe primary windings 112 and 116. As shown in FIG. 2, the capacitor C1and the inductor L1 are series-connected between the primary winding 112and a node defined between the switches Q1 and Q2.

The power converter 200 includes a single rectifier 134 coupled betweenthe output terminals 104 and the secondary windings 114 and 118. Asshown in FIG. 2, the secondary windings 114 and 118 are directly coupledin parallel, prior to the rectifier 134. Therefore, the rectifier 134 iscoupled between the output terminals 104 and the parallel-connectedsecondary windings 114 and 118.

Although FIG. 1 illustrates one rectifier 134 or 136 coupled at anoutput of each secondary winding 114 and 118, and FIG. 2 illustrates asingle rectifier 134, other embodiments may include more or less (orzero) rectifiers, rectifiers positioned in other circuit arrangements,etc.

Referring again to FIG. 1, the switches Q1 and Q2 are illustrated asarranged in a half-bridge circuit, but other embodiments may include LLCconverters including more or less switches, switches connected indifferent circuit arrangements (e.g., full-bridge circuits), etc.

The input terminals 102 and the output terminals 104 may include anysuitable connector, terminal, wire, conductive trace, etc. for receivinga power from a voltage source or supplying power to a load. For example,the input terminals 102 may be connected to receive an input voltagefrom a DC voltage source, from a pre-regulator output, etc. AlthoughFIG. 1 illustrates two input terminals 102 and two output terminals 104,other embodiments may include more or less input and output terminals.

An interleaved LLC power converter according to another exampleembodiment of the present disclosure is illustrated in FIG. 3 andindicated generally by reference number 300. The power converter 300includes input terminals 202 for receiving an input voltage from avoltage source, and output terminals 204 for supplying an output voltageto a load.

The power converter 300 also includes an LLC converter 206 coupled toreceive the input voltage from the input terminals 202 and supply theoutput voltage to the output terminals 204. The LLC converter 206includes a transformer 210. The transformer 210 includes a first windingset including a primary winding 212 and a secondary winding 214, and asecond winding set including a primary winding 216 and a secondarywinding 218.

As shown in FIG. 3, a spacer 220 is positioned between the first set ofwindings 212 and 214, and the second set of windings 216 and 218. Theprimary windings 212 and 216 are coupled in series, and the secondarywindings 214 and 218 are coupled in parallel via the rectifiers 234 and236.

The power converter 300 further includes an LLC converter 208interleaved with the LLC converter 206 (e.g., the LLC converts 206 and208 are coupled in parallel with one another between the input terminals202 and the output terminals 204, etc.). The LLC converter 208 includesa transformer 222. The transformer 222 includes a first winding setincluding a primary winding 224 and a secondary winding 226, and asecond winding set including a primary winding 228 and a secondarywinding 230.

As shown in FIG. 3, a spacer 232 is positioned between the first set ofwindings 224 and 226, and the second set of windings 228 and 230. Theprimary windings 224 and 228 are coupled in series, and the secondarywindings 226 and 230 are coupled in parallel via the rectifiers 238 and240.

As illustrated in FIG. 3, the LLC converter 206 includes two switches Q1and Q2, two capacitors C1 and C2, and an inductor L1. The switches Q1and Q2, the capacitors C1 and C2, and the inductor L1 are coupledbetween the input terminals 202 and the primary windings 212 and 216.Specifically, the switches Q1 and Q2 are coupled in parallel with thecapacitors C1 and C2, and the inductor L1 is coupled between thecapacitors C1 and C2 and the primary windings 212 and 216.

The LLC converter 206 also includes a rectifier 234 coupled between thesecondary winding 214 and the output terminals 204, and a rectifier 236coupled between the secondary winding 218 and the output terminals 204.The rectifiers 234 and 236 are coupled in parallel, and may include anysuitable rectifier circuit such as a full-bridge rectifier, etc.Although FIG. 3 illustrates two rectifiers 234 and 236, in otherembodiments the secondary windings may be connected in a center-tappedtransformer circuit arrangement, etc.

The LLC converter 208 includes two switches Q3 and Q4, two capacitors C3and C4, and an inductor L2. The switches Q3 and Q4, the capacitors C3and C4, and the inductor L2 are coupled between the input terminals 202and the primary windings 224 and 228. The switches Q3 and Q4 and coupledin parallel with the capacitors C3 and C4, and the inductor L2 iscoupled between the capacitors C3 and C4 and the primary windings 224and 228.

The LLC converter 208 also includes a rectifier 238 coupled between thesecondary winding 226 and the output terminals 204, and a rectifier 240coupled between the secondary winding 230 and the output terminals 204.The rectifiers 238 and 240 are coupled in parallel, and may include anysuitable rectifier circuit such as a full-bridge rectifier, etc. Becausethe primary windings in each LLC converter 206 and 208 are connected inseries while the secondary windings are connected in parallel via therectifiers, current may be shared among the secondary windings in eachLLC converter.

The controller(s) may be configured to control switching operation ofthe switches Q1-Q4 of the LLC converters 206 and 208 to operate the LLCconverters 206 and 208 with a ninety degree phase shift relative to oneanother.

Although FIG. 3 illustrates two interleaved half-bridge LLC converters206 and 208 in the power converter 200, other embodiments may includemore or less LLC converters, other converter topologies, etc. The LLCconverters may be operated with different phase shifts relative to oneanother, such as ninety degree phase shifts, sixty degree phase shifts,forty-five degree phase shifts, etc. The number and degree of phaseshifts may correspond to a number or LLC converters in the powerconverter 300.

The transformers 110 and 210 are example embodiments, and the powerconverters 100, 200, 300 described herein may include suitabletransformer(s) other than the transformers 110 and 210, includingdifferent numbers of cores, different core constructions, differentwinding patterns, etc.

FIG. 4 illustrates an exploded view of a transformer 310 according toanother example embodiment of the present disclosure. The transformer310 includes a core 342. A primary winding 314, a secondary winding 316,and a spacer 320 are positioned about the core 342.

The transformer 310 has a 4:2 turns ratio. The primary winding 314includes four layers of planar windings, with one turn per layer. Thefour layers of the primary winding 314 are connected in series for atotal of four turns in the primary winding 314. The secondary winding316 also includes four layers of planar windings, with one turn perlayer. Two series connected layers are connected in parallel to definetwo turns total in the secondary winding 316, for a 4:2 turns ratio(e.g., a 2:1 turns ratio).

The spacer 320 is positioned between two sets of the primary winding 314and the secondary winding 316, each with a 1:1 ratio including twoprimary turns and two secondary turns, to create loose coupling (e.g.,magnetic coupling) between the two sets. The spacer 320 may include anysuitable material for separating the winding layers with loose coupling,such as plastic, FR4 printed circuit board material, etc. The spacer 320may include a disc, circle, etc. having a same dimension, perimeter,footprint, etc. as each winding.

In some embodiments, multiple transformers each with a 1:1 ratio may beused to achieve a desired turns ratio. For example, four transformerseach with a 1:1 turns ratio may be connected with the primary windingsin series, and the secondary windings connected in parallel directly orvia rectifiers, in order to achieve a 4:1 turns ratio. In other,embodiments, the primary windings could be connected in parallel withthe secondary windings connected in series directly or via rectifiers,to define a step-up turns ratio (e.g., a 1:4 step-up turns ratio, etc.).

FIG. 5 illustrates an exploded view of a transformer 410 according toanother example embodiment of the present disclosure. The transformer410 includes a transformer core 442. Primary windings 414, secondarywindings 416, and spacers 420 are positioned around the transformer core442.

Specifically, FIG. 5 illustrates four coils of the primary winding 414separated from one another by three spacers 420. Each coil of theprimary winding 414 includes two turns, and the primary winding coilsare connected in series.

The secondary winding 416 includes four coils, with each coil having twoturns corresponding to a different one of the four coils of the primarywinding 414. The four sets of primary and secondary coils with 1:1 turnsratios having two turns each are separated from one another by the threespacers 420. Each coil of the secondary winding 416 includes two turns,and the secondary winding coils are connected in parallel directly orvia rectifiers.

Because the primary winding 414 includes four sets of coils connected inseries with two turns per coil, and the secondary winding includes fourset of coils connected in parallel with two turns per coil, thetransformer 410 has an 8:2 (e.g., 4:1) turns ratio. In general, an Nnumber of winding sets having a 1:1 turns ratio may be connectedtogether to define an N:1 turns ratio.

FIG. 5 illustrates each coil as including two planar turns. In otherembodiments, other suitable primary and secondary winding coilarrangements may be used, including more or less coils, more or lessturns per coil, more or less spacers 420, non-planar wires, etc.

The transformer 410 also includes an integrated resonant inductor 444.Integrating the resonant inductor 444 in the transformer 410 may improvea volume of the transformer, reduce losses in the transformer 410, etc.For example, an LLC portion of the power converter may have any suitablepower density depending on a power level of the power converter, such asat least 100 W per cubic inch, etc.

FIG. 6 illustrates a transformer 510 according to another exampleembodiment of the present disclosure. The transformer 510 includes atransformer core 542. The core 542 may include any suitable material,including ferromagnetic material, etc.

A first set of windings includes a primary winding 512 and a secondarywinding 514, each wound about the transformer core 542. A second set ofwindings includes a primary winding 516 and a secondary winding 518,each wound about the transformer core 542.

Although FIG. 6 illustrates a specific winding layout of the primary andsecondary windings about the core 542, other embodiments may include anysuitable transformer construction, such as a three-phase LLC integratedtransformer, etc. The core 542 may include any suitable number of legs,any suitable connection arrangement of the legs, etc.

A spacer 520 is positioned between the first and second sets of windingsto separate the first and second sets of windings. Due to the positionof the spacer 520, a magnetic coupling between the two sets of windingsis less than a magnetic coupling between the primary winding 512 and thesecondary winding 514, and less than a magnetic coupling between theprimary winding 516 and the secondary winding 518.

As shown in FIG. 5, the primary windings 512 and 516 are coupled inseries, and the secondary windings 514 and 518 are coupled in parallel.If the primary windings 512 and 516 have the same number of turns as thesecondary windings, the transformer 510 should have a two to onestep-down turns ratio.

In other embodiments, the primary windings 512 and 516 may be coupled inparallel, and the secondary windings 514 and 518 may be coupled inseries (e.g., directly, via rectifiers, etc.). In that case, if each ofthe windings has the same number of turns, the transformer 510 shouldhave a one to two step-up turns ratio.

Connecting the primary windings in parallel while connecting thesecondary windings in series (e.g., directly, via rectifiers, etc.), maydefine a step-up turns ratio for power converters used in step-upapplications. For example, if the transformer includes eight sets of 1:1windings with the primary windings coupled in parallel and the secondaryrectifiers coupled in series, a 1:8 turns ratio may be defined. If theinput voltage is 48V, an output voltage of 384V may be generated withthe 1:8 transformer ratio using a full bridge interleaved LLC converter.Using a half-bridge interleaved LLC converter, the same 1:8 turns ratioshould provide a 192V output. In general, an N number of winding setshaving a 1:1 turns ratio may be connected together to define a 1:N turnsratio for a converter.

In other embodiments, there may be more or less than two sets ofwindings and the number of turns in each winding may be different, theremay be more or less than two sets of windings, so the step-up orstep-down turns ratio of the transformer 510 may be varied.

The transformer 510 may be used in any suitable application, such asincorporated in a switch-mode DC-DC power converter (e.g., powerconverters 100, 200 and 300 described herein, push-pull converters,forward converters, half-bridge converters, full-bridge converters,pulse width modulation (PWM) converters, etc.).

As described herein, the example power converters and controllers mayinclude a microprocessor, microcontroller, integrated circuit, digitalsignal processor, etc., which may include memory. The power convertersand controllers may be configured to perform (e.g., operable to perform,etc.) any of the example processes described herein using any suitablehardware and/or software implementation. For example, the powerconverters and controllers may execute computer-executable instructionsstored in a memory, may include one or more logic gates, controlcircuitry, etc.

Example embodiments described herein may be used in any suitable powerconverter application, such as a single rail resonant bus converter, aninterleaved resonant bus converter, a fixed frequency resonant busconverter, a buck-fed converter, a boost-fed converter, a buck-boost-fedLLC converter, hyper scale applications, telecommunicationsapplications, open compute project (OCP) power for data centers, serverspower supplies, etc.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

1. An interleaved LLC power converter, comprising: one or more inputterminals for receiving an input voltage from a voltage source; one ormore output terminals for supplying an output voltage to a load; a firstLLC converter including a first transformer and a first spacer, thefirst transformer coupled between the input and output terminals, thefirst transformer including a first plurality of winding sets eachincluding a primary winding and a secondary winding magnetically coupledwith one another, the first spacer positioned to separate an adjacentpair of the first plurality of winding sets, the primary windings of thefirst plurality of winding sets connected in series and the secondarywindings of the first plurality of winding sets connected in parallel;and a second LLC converter interleaved with the first LLC converter, thesecond LLC converter including a second transformer and a second spacer,the second transformer coupled between the input and output terminals,the second transformer including a second plurality of winding sets eachincluding a primary winding and a secondary winding magnetically coupledwith one another, the second spacer positioned to separate an adjacentpair of the second plurality of winding sets, the primary windings ofthe second plurality of winding sets connected in series and thesecondary windings of the second plurality of winding sets connected inparallel.
 2. The power converter of claim 1, wherein each LLC converterincludes at least two switches, a capacitor and an inductor, and theswitches, capacitor and inductor are coupled between the one or moreinput terminals and the transformer of said LLC converter.
 3. The powerconverter of claim 2, further comprising a controller for controllingswitching operation of the switches of the first and second LLCconverters to operate the first and second LLC converters with one of aforty-five degree phase shift, a sixty degree phase shift, and a ninetydegree phase shift, relative to one another.
 4. A transformer,comprising: at least one core; a plurality of winding sets wound aboutthe at least one core, each winding set including a primary winding anda secondary winding magnetically coupled with one another, the primarywinding and the secondary winding including the same number of turns,the primary windings of the plurality of winding sets connected inseries and the secondary windings of the plurality of winding setsconnected in parallel to define a step-down turns ratio of thetransformer or the primary windings of the plurality of winding setsconnected in parallel and the secondary windings of the plurality ofwinding sets connected in series to define a step-up turns ratio of thetransformer; and at least one spacer positioned to separate an adjacentpair of the plurality of winding sets, a magnetic coupling between theadjacent pair of the plurality of winding sets less than the magneticcoupling between the primary winding and the secondary winding withineach winding set.
 5. The transformer of claim 4, wherein the primarywindings of the plurality of winding sets are connected in series andthe secondary windings of the plurality of winding sets are connected inparallel to define the step-down turns ratio of the transformer.
 6. Thetransformer of claim 4, wherein the primary windings of the plurality ofwinding sets are connected in parallel and the secondary windings of theplurality of winding sets are connected in series to define the step-upturns ratio of the transformer.
 7. The transformer of claim 4, whereinthe plurality of winding sets comprises exactly two winding sets and theturns ratio of the transformer is two to one or one to two.
 8. Thetransformer of claim 4, wherein the plurality of winding sets comprisesexactly four winding sets and the turns ratio of the power converter isfour to one or one to four.
 9. The transformer of claim 4, wherein eachwinding comprises a planar winding including one turn per layer.
 10. Thetransformer of claim 4, further comprising a resonant inductor coilintegrated with the core.
 11. The power converter of claim 1, whereinthe first and second pluralities of winding sets each comprise exactlytwo winding sets, and a turns ratio of each LLC converter is two to one.12. The power converter of claim 1, wherein the first and secondpluralities of winding sets each comprise exactly four winding sets, anda turns ratio of each LLC converter is four to one.
 13. The powerconverter of claim 1, wherein each winding comprises a planar windingincluding one turn per layer.